import rclpy 
from rclpy.node import Node

def main():
    rclpy.init ()#初始化工作，分配资源
    node = Node ("python_node") 
    node.get_logger().info('你好Python节点! ')
    node.get_logger().warn('你好Python节点! ')
    rclpy.spin (node)
    rclpy.shutdown ()